1. Field of the Invention
The present invention relates to a method of repairing a mask for use in lithographic manufacturing of semiconductors and in particular, to a method of repairing phase shift transmission masks.
2. Description of Related Art
Photolithography processes for producing semiconductors and the like utilize masks which are formed by deposition of materials opaque to the light or energy source to be utilized in a desired pattern on a substrate which is generally transparent to such light or energy source (hereinafter referred to generally as light). The mask pattern is transferred via spatially modulated light to create an aerial image which is transferred to a resist film on a substrate. After being exposed to the pattern, the resist film is contacted with a developer and subsequently an etchant to create the desired structure on the substrate.
As a consequence, any defects present on the mask may be transferred onto the substrate and result in defects in the final desired structure. Materials such as chromium, chromium oxide, tungsten and nickel are typically used for photo masks and formed in layer thicknesses of appropriately 500 angstroms to 1000 angstroms on a transparent substrate, such as a quartz glass substrate.
Phase shift masks also utilize additional transparent layers applied to the mask to apply a phase difference of 1800 to the light being transmitted. When used on alternate transparent areas of the mask, such phase shifters reduce the minimum pattern resolution substantially, as compared to the photo mask method.
Methods of repairing mask used to produce semiconductors have been described in the prior art for example, as U.S. Pat. Nos. 5,318,869, 5,246,804, and 4,906,326. In particular, the prior art discloses various methods of adding or removing material from a mask to repair defects, such as in U.S. Pat. Nos. 5,468,337, 5,443,931, 5,382,484, 5,273,849, and 5,080,597. In particular, the '337, '391, '484 and '957 patents relate to repair of phase shift masks.
Despite the numerous prior art in this area, known methods of repairing phase shift masks utilize time consuming trial and error methods of adding the materials required to effect the repairs to the mask itself.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method and system for repairing semiconductor masks, including phase shift masks, wherein trial and error techniques are not utilized.
It is another object of the present invention to provide a method or system of repairing such masks by providing a methodology that allows the matching of patch parameters to the desired repair area to ensure a quality repair process.
It is a further object of the invention to provide a method and system for repairing masks which reduces misalignment, overlap geometry transmission and phase errors in patches added to the mask.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.